Twin probes enter space to spy on the Sun

One stereo spacecraft will orbit the Sun ahead of the Earth, one behind, in order to generate a 3-D view

(Image: JHU Applied Physics Laboratory)

NASA’s STEREO mission to study the Sun in three dimensions successfully blasted into space on Wednesday, sending twin solar observatories into orbit.

The two-year Solar Terrestrial Relations Observatory (STEREO) mission will be the first to view the Sun from two separate vantage points outside the Earth’s orbit.

The nearly identical satellites will act like a pair of human eyes, each picking up data that will be correlated with data from observatories on the ground and in low-Earth orbit. The result will be a 3D view of the Sun’s eruptions and their impact on the Earth.

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A three-stage Boeing Delta II rocket carried the observatories into orbit from the Cape Canaveral Air Force Station in Florida, US, at 2052 EDT (0052 GMT on Thursday). Lift-off took place during the last minute of a 15-minute launch window that opened at 2038 EDT.

The twin spacecraft, each about the size of a golf cart and weighing some 620 kilograms (1364 pounds), separated without problem from the rocket after launch, NASA said.

NASA said it should have the first 3-D images from the spacecraft, which are each equipped with 16 instruments, in mid-December.

Broadside view

“We are at the dawning of a new age of solar observations,” Russ Howard of the US Naval Research Laboratory said at a NASA news conference on Tuesday. “We’re going to be viewing things in a new dimension for us.”

Howard said STEREO would have an unprecedented “broadside” view of the entire relationship between the Sun and the Earth.

Scientists hope the mission will glean insight into solar activities such as coronal mass ejections (CMEs), the most violent explosions in the solar system.

When aimed at Earth, these billion-tonne eruptions of the Sun’s outer atmosphere spew intense radiation, severely disrupting the Earth’s environment and endangering astronauts and scientific spacecraft.

Information gleaned on the origin and behaviour of CMEs should allow more accurate forecasting of solar activity. That would improve planning for space missions as well as satellite communications and video transmissions.

Pinball flipper

At first the twin observatories will be placed in a highly eccentric Earth orbit, NASA said.

After a few weeks, the two spacecraft – named “A” for “Advance”, and “B” for “Behind” –are expected to drift slowly apart but stay relatively close to each other as they line up for a flyby of the Moon about one month into the mission.

“This is when the relatively small distance between the two spacecraft makes all the difference,” the space agency said on its website.

NASA will use the Moon’s gravity like a pinball flipper to send them into opposite and slightly distinct orbits around the Sun.

“Behind” will be flung completely away from the Earth and will become a satellite of the Sun, while the “Ahead” spacecraft will curve back to fly past the Moon a second time six weeks later, when it will be flung out in the opposite direction.

The total cost of the mission is &dollar;550 million, NASA said. Scientists from Belgium, the UK, France and Germany are also participating in the mission.